On the Metabolic Conversion of Salicortin-like Chemical Defenses (Salicortinoids) in the Lepidopteran Specialist Herbivore Cerura vinula (Notodontidae)

Abstract

The lepidopteran specialist herbivore Cerura vinula (Notodontidae) has adapted to thrive on poplar and willow species (Salicaceae). Previous research showed that C. vinula uses a unique mechanism to detoxify the host plant’s defense compounds. After discovering a reductively transformed derivative of tremulacin (6’-O-benzoyl-salicortinol) isolated from the frass of C. vinula, we assessed the chemical stability of salicortin-like defenses (salicortinoids) and analyzed their decomposition products over time and at different pH values. We then incubated uniformly 13C-labeled compounds in vitro with mid-gut homogenates of C. vinula larvae to determine the metabolism of salicortinoids. The key to the metabolic process, we found, is the initial reductive transformation of the salicortinoids; this step reduces the formation of toxic catechol.